This invention relates to a battery electrode, a secondary electrode and a method of manufacturing this electrode and battery.
The electrodes of a secondary battery according to the prior art generally are manufactured using an organic binder or a binding agent for the sake of shape retention. A battery electrode that uses an organic binder or a binding agent, a secondary battery that employs such battery electrodes and a method of manufacturing the electrodes and secondary battery according to the prior art will now be described.
FIG. 3 is a diagram schematically illustrating a conventional secondary battery electrode that uses an organic binder. More specifically, FIG. 3 is an enlarged sectional view of the electrode taken in the direction of collector thickness. The electrode depicted in FIG. 3 is obtained by binding an active material 8 and carbon particles 9 to the surface of a collector 7 by an organic binder 10. An organic polymer in which adsorption and desorption of protons participates in the oxidation-reduction reaction of a positive electrode or negative electrode is used as the active material 8.
The electrode is formed by applying the electrode mixture to the surface of the collector and then drying the same. The electrode mixture consists of the aforesaid organic polymer serving as the active material, carbon powder serving as a conduction aid, and the organic binder for binding the polymer and powder together. The organic binder is an organic polymer that does not exhibit electron conductivity and has absolutely no proton conductivity.
The conventional secondary battery has two electrodes fabricated in the above-described manner, and the two electrodes are arranged to oppose each other across an electrolyte and separator. The secondary battery is fabricated by bringing the two electrodes into opposition via the electrolyte and separator.
In the course of investigations toward the present invention the following problems have been encountered.
The conventional battery electrode manufactured using an organic binder is disadvantageous in that the efficiency of active material utilization is low as well as the yielding rate of capacity (e.g., capacity yield per unit weight). The reason for this is that the organic binder scattered on the surface of the active material impedes the conduction of protons and electrons and makes it difficult for the oxidation-reduction reaction to proceed.
Further, the method of manufacturing the conventional battery electrode using the organic binder is inadequate in terms of film manufacturing workability and productivity when the electrode is fabricated. The reason for this is that the above-mentioned electrode mixture tends to coalesce and experience a decline in fluidity owing to the use of the organic binder. Furthermore, electrode film thickness and electrode weight tend to be non-uniform, making it difficult to suppress variations in battery capacity from one battery to another.
Accordingly, an object of the present invention is to provide a battery electrode and a secondary battery in which an improvement in efficiency of active material utilization and yielding rate of capacity are achieved.
Another object of the present invention is to provide a battery electrode manufacturing method and secondary battery manufacturing method featuring improved film manufacture workability and productivity at the time of electrode fabrication.
Further objects of the invention will become apparent in the entire disclosure.
A battery electrode according to a first aspect of the present invention includes at least one type of organic polymer and a carbon material which serves as a conduction aid, wherein the organic polymer is, in its entirety, a compound which produces an oxidation-reduction reaction due to electrochemical proton adsorption and desorption.
A battery electrode according to a second aspect of the present invention includes a dried product of a solution containing at least one type of organic polymer in dissolved form and powder of a carbon material, wherein the organic polymer is, in its entirety, a compound which produces an oxidation-reduction reaction due to electrochemical proton adsorption and desorption.
In a third aspect of the present invention, a secondary battery uses a battery electrode according to the present invention as a positive electrode, a negative electrode or both.
In a fourth aspect of the present invention, a method of manufacturing a battery electrode includes at least a step of forming a dried product of a solution containing at least one type of organic polymer in dissolved form and powder of a carbon material, wherein a compound which produces an oxidation-reduction reaction due to electrochemical proton adsorption and desorption is used as the entirety of the organic polymer.
In a fifth aspect of the present invention, a method of manufacturing a secondary battery includes using a battery electrode, which has been manufactured by the method of manufacturing a battery electrode according to the present invention, as a positive electrode, a negative electrode or both.